One woman thought she found the perfect place to rent, then the homeowner returned from vacation.

Angel Sheppard had big plans to spruce up the foreclosed Towson home she bought in June, but right after buying the place Sheppard noticed someone already started making her new house a home.

There was an air conditioner in the window and the blinds were down.

"It made me a little uneasy," Sheppard recalled. "I hadn't even moved in yet."

Sheppard called her real estate agent, and the two knocked on the door. A young woman with two children had been living there for nearly a week, but it turns out she was the victim of a rental scam. Someone claiming to represent the owner rented it to her for $1,500 cash.

Baltimore County police have seen a handful of similar incidents in Parkville, White Marsh and Overlea, one reported as recently as Aug. 11. Neighboring police departments said they hadn't received similar reports — but rental scams are nothing new. And as the ways to rent proliferate, so do the ways to scam.

Nationally, rental and real estate scams rose 11 percent over the past two years, to 11,562 victims in 2015 from 10,384 victims in 2013, according to the FBI's annual Internet Crime Report, which is based on data collected through the Internet Crime Complaint Center. The category also includes real estate investment fraud; scams involving home mortgages, refinancing, short sales and foreclosures; and property involved in money laundering, such as a grow house.

Last year, 222 Marylanders were victims of such scams, at a cost of $657,500. Nationally, real estate and rental scams cost victims $41.4 million in 2015.

"People just need to really be cautious and diligent about their research," said Anita Davis, the president-elect of Greater Baltimore Board of Realtors. "They're publishing phone numbers, they're answering the phone."

Davis, an associate broker for Long and Foster who works in Baltimore County, recalled one time, six or seven years ago, when a client's for-sale home popped up on Craigslist as a rental.

The homeowner, Davis' client, took matters into his own hands and responded to the ad, talked to a man who said he was a missionary on assignment in a foreign country. He'd send the key once he received a $700 deposit in the mail.

Davis' client confronted him, "and then there was a click on the other end of the line," Davis said.

In another incident, a few years ago, the scammer made up an email address using the owner's name, to fool any prospective renters diligent enough to check the property record, she said.

The rise of vacation rental sites, most notably Airbnb has added to the ways renters can be scammed.

Airbnb renters have lost hundreds of dollars — and had vacation plans ruined — by paying outside the rental website's secure online system, booking properties that don't exist or accidentally clicking over to a scammer's website that is a near mirror image of the legitimate one. Other vacation rental websites, such as HomeAway, also have been subject to scams.

On its website, Airbnb advises renters to read listings carefully and strike up a conversation with potential hosts, to establish clear expectations for the stay and get a better sense of whether anything seems off. Airbnb encourages users to communicate and pay only through the website, and warns against personal email correspondence and wire transfers.

Craigslist, too, has a page on its website warning people about scams and offering advice about how to avoid being victimized: stick to local deals, insist on face-to-face transactions, say no to wire transfers and don't rent a place you haven't seen.

Still, too often victims look past potential red flags because they are emotionally invested in securing the home or apartment, said Dan Daugherty, CEO of Denver-based Rentbits.com, a marketing website that lists properties for rent.

"They have a fear of losing this 'great deal,' and if they don't act now they will pay a significantly higher rental rate with someone else," Daugherty wrote in an email.

In March, researchers in the New York University Tandon School of Engineering published a study that found Craigslist had failed to identify more than half of scam rental listings. The study also found postings that were reported as suspicious would remain on the website for as long as 20 hours before they were removed. Craigslist officials did not respond to multiple requests for comment.

Meanwhile, justice can be elusive for both renters and homeowners.

Police try to work with the homeowner or bank, if the property is bank-owned, to negotiate a deal for victims to stay at the home until they find somewhere else to go, said Det. Larry Rogers, who has been investigating rental scams in Baltimore County.

In one case, Rogers helped negotiate a deal to allow three men who unwittingly rented a foreclosed duplex to stay there for 30 days, until they found somewhere else to live. Having already lost nearly $5,000 to scammers, the victims did not have to pay rent for the additional time they stayed at house.

Renters who want their money back must know who scammed them and go to court.

"Getting money back immediately is difficult because of the court process," Rogers said. "It takes time."

Without police intervention, homeowners dealing with renters who don't want to leave also may have to take their case to court and file for an eviction notice, a process that can take up to 30 days, Rogers said.

The woman in Sheppard's house didn't put up a fight.

"She told me she had been scammed on Craigslist," Sheppard said. "After the police came and I showed them my paperwork that I was the owner, she left."

The woman told Baltimore County police she had responded to a Craigslist rental advertisement for the home, signed a contract with a "Sarah Kostner" of "S & K Reality LLC," and paid a someone named "Sam" $1,500 cash to move in Memorial Day.

Neither "Sarah Koster" nor "S & K Reality LLC" existed, according to the police report filed on the matter June 3. The person she paid the deposit, "Sam" — who police described as a tall man of possibly mixed race with sandy brown dreadlocks — disappeared with no known address or last name.

Police believe he's their main suspect and that he broke into the home through a basement window, changed the locks, made new keys and gave one to the victim.